A homeless man who used the cellphone of a missing college student has been questioned by the NYPD.

John Koppinger was arrested Tuesday night on warrants unrelated to the disappearance of Patrick Welsh, 22, a student at York College in Pennsylvania, who was last seen at the Harrisburg train station on April 15.

Koppinger told cops he found the phone on University Avenue in The Bronx, and called a relative with it, sources said.